As a sustainable clean energy, solar energy is an ideal renewable energy. Due to low energy density, poor continuity in energy reception, variability with seasons, day and night and climate, solar energy is mainly applied in fields that have low requirements in energy density, allow discontinuity of light collecting and have scattered customers, such as solar water heaters and solar greenhouses. It is an effective way to save mineral resources, reduce CO2 emission, ensure energy safety and realize sustainable development by putting great efforts in developing solar photovoltaic power generation and solar photo-thermal power generation.
The chief factors inhibiting solar photovoltaic power generation are high costs in photovoltaic conversion, great fluctuation in power generation capacity and inconvenience in long distance transmission. If the weather conditions are the same, solar tracking techniques would enable solar cells constantly perpendicular to sunlight, which is beneficial in enhancing utilization of solar energy and can increase power generation capacity while prolonging power generation period, and which is also effective in mitigating effects on grid fluctuation to some extent while reducing costs of solar photovoltaic power generation. In light of the above reasons, solar tracking techniques arrest high attention.
Tracking techniques can be generally categorized into three types on the basis of the means of generating control signals by a control unit, i.e. active tracking, passive tracking and hybrid tracking. Tracking techniques can also be categorized into uni-axial tracking and bi-axial tracking according to the number of rotary shafts in a rotary stage-adjusting member. Tracking techniques, by combining the above two categorizations, may be categorized into active uni-axial tracking, active bi-axial tracking, passive uni-axial tracking, passive bi-axial tracking, hybrid uni-axial tracking and hybrid bi-axial tracking.
Universal problems in current tracking techniques are: high energy consumption in driving and operation, and poor stability and high manufacturing costs of tracking devices. The main reasons are that the central support post of the tracking devices serves the following three functions simultaneously: a support for total gravities, a rotary center, an acting point of the reacting force of the tracking driving force, and even an acting point of the tracking driving force itself. Therefore, current solar tracking techniques are limited in utilization of solar energy.